Isotropic liquid detergents for use in laundry comprise varying concentration levels of surfactant. 10 to 15% wt is commonplace in Portugal and Spain, 18 to 27% wt typical in the Benelux countries, Germany and Italy, while levels of 35 to 40% wt surfactant have been used in the UK and France.
While moderately concentrated detergent compositions for laundry use have been known from the literature and available in the marketplace for some time, there has been a recent trend towards more concentrated liquid products and a “three-times concentrate” (Persil™ “Small and Mighty”) was launched, in the UK. The dosage instructions for this product suggest that 35 ml of the composition should be used for a normal product load. With less concentrated products volume dosages are typically higher, so as to reach the same in-wash concentrations of non-soap surfactant.
Reasons for this trend towards concentrated products have included a desire to make more environmentally friendly products, which use less packaging, require fewer chemicals for their manufacture and require less energy to manufacture and transport them. Concentrated products also offer the advantages of taking up less shelf and storage space. Concentrated products deliver the same level of surfactant into the wash liquor from a smaller volume of product, and they are generally formulated by taking water out.
However, there are limits to the extent to the benefits which can be obtained by simply concentrating products. Particular problems occur with dispensing and delivery of products. For example, at particularly high concentrations liquid products may exhibit unacceptable or unstable viscosities and solid products may exhibit hydroscopicity and poor flow or caking. These known disadvantages, such as maintenance of product stability, pourability and product appearance have lead to a number of proposals.
A “four times” concentrate has been launched in Australia under the brand name “Orange power” and is described as “a 4× concentrate enzyme liquid detergent”. Its dosage recommendation is 25 ml (a capful) for top loading washing machines and ¾ of a cap for front loaders.
Unit dosage has been suggested to overcome some of the known problems but this can lead to dissolution problems. Moreover, rising cost of surfactants, especially those from oil-based materials has led to pressures to remove surfactant as well.
WO 2004/074419 (Novozyme) suggests she replacement of part of the surfactant, builder, bleach, and fillers in a detergent with enzymes. This is said to result in a significant reduction of the volume and weight of the detergent necessary for one wash. After partial replacement by enzymes, levels of surfactant of less than 30 wt % preferably 4 to 20 wt %, more preferably 5 to 15 wt % are disclosed. Any soil suspending polymer is said to foe reduced to 0 to 6 wt % after it too is partially or fully replaced by enzymes. Lipase is used to boost oily soil detergency. In the examples in-wash non-soap surfactant levels as low as 0.18 g/L are disclosed. The drawback with the approach suggested in this document is that it is too dependent on enzymes which are expensive and are sensitive to storage and use conditions. Furthermore the stains selected to exemplify cleaning are apparently chosen to be responsive to enzymes and consequently do not demonstrate the solution to the more realistic problem of detergency against everyday dirt and stains, such as clay.
WO 2006/113314 (P&G) discloses a liquid laundry detergent composition comprising:    (a) from about 5 to about 20000 LU/g of a “first wash” lipase, which is a polypeptide having an amino acid sequence which has at least 90% identity with the wild-type lipase derived from Humicola lanuginosa strain DSM 4109, and,    (b) from about 0.01 wt % to about 10 wt % by weight of the composition of a modified polyethyleneimine polymer which comprises a polyethyleneimine backbone of about 300 to about 10000 weight average molecular weight; and    (c) the balance of the composition comprising a liquid carrier.
This patent publication states that alkyl ethoxy sulfate surfactant may be present in the composition from about 5% to about 30%; or from about 7% to 16% by weight of the composition. Additional surfactants include up to 7% of nonionic and/or anionic co-surfactants. Aqueous washing solutions are disclosed to comprise 500 to 7,000 ppm (0.5 to 7 g/L) of the composition, preferably 1000 to 3000 ppm. If the non-soap surfactant level varies from 11 to 21 wt %, as in the examples, this would provide a preferred wash solution non-soap surfactant concentration of from 0.1 to 0.6 g/l. Although the general disclosure allows for high levels of EPEI, the actual levels used are too low to realise the benefit from the low dose of surfactant to the wash from a low volume dose of the composition.